The present invention concerns an artillery-shell rammer with a carriage provided with a shell-accommodation trough aligned with the weapon""s chamber behind the barrel and having a shell positioner at the rear, wherein the carriage travels back and forth on a rail along a track paralleling the axis of the barrel and is coupled to a drive mechanism that accelerates it toward the barrel, and wherein means of braking the carriage are provided at a prescribed distance back of the barrel.
A shell rammer of this genus, a xe2x80x9cfree-flightxe2x80x9d rammer, is known from European Published Application 0 352 584 A2 for example.
The principle of a free-flight shell rammer is that a shell outside the weapon can be accelerated to the extent that, once it has left the accelerating system, it will continue moving in free flight due to the kinetic energy provided thereby and accordingly rammed into position. The accelerating system employed in the free-flight shell rammer disclosed in the aforesaid publication, and in CH 684 627 as well for example, includes a carriage. A shell is laid in the carriage and is accelerated along with it. Upon attaining sufficient velocity, the carriage is braked. The shell flies through the weapon""s breechblock and into the chamber and rams in at the barrel""s grooves.
Artillery weapons usually do not have a take-off ramp long enough to accelerate the carriage and its load to the velocity needed to ram the shell. Rapid accelerations must be obtained by calculating from the available strip and from the prescribed velocity. To accelerate the existing masses (the carriage and the shell) absolutely requires a powerful impact, which must be applied suddenly. Hence, a high energy density must be briefly accessible for the acceleration procedure.
Known free-flight shell rammers employ pneumatic (U.S. Pat. No. 4,957,028) or hydraulic (CH 664 627) drives equipped with piston-and cylinder mechanisms.
The fluid is stored in a reservoir and provided instantaneously to the drive through a special valve.
The requisite pneumatic or hydraulic pressure is generated by a motor-powered compressor or hydraulics assembly.
The electric energy is converted into another form, demanding considerable expenditure to process and store and entailing considerable loss of efficiency.
Also known are free-flight shell rammers driven by resilient energy accumulators, motor-compressed helical springs or gas bladders for instance, mechanically released to initiate acceleration and forward the requisite energy by way of downstream components (chains or racks e.g.) to the shell or carriage.
The object of the present invention is accordingly an improved shell rammer for the artillery of the type hereinbefore wherein electrical energy is converted directly into kinetic energy within the drive mechanism, eliminating the loss of efficiency characteristic of systems that convert electrical energy into another form.
The invention derives from the realization that it would be impossible to build a conventional electrically powered drive mechanism that could generate enough energy at once to propel the carriage straight forward at precisely the instant the shell is to be rammed. Converting the rotary motion characteristic of conventional motors rapidly enough into the translatinal motion required by the carriage would strain the components (chains, shafts, cogwheels, and racks) generally employed to build such machinery to the limits of their endurance, given the inertia of the masses that have to be instantaneously accelerated. Furthermore, the mere size and weight of a motor theoretically powerful enough to accomplish the task would almost entirely prevent its installation in a combat vehicle, on a moving loading arm for instance.
This object is attained in accordance with the present invention in a shell rammer of the aforesaid genus in that the drive mechanism is provided with at least one linear motor.
It has been demonstrated especially practical for the motor""s primary section, the section the electric current is supplied to, that is, to be fastened stationary to the carriage track and for the secondary section to be fastened stationary to the carriage.
The secondary section can be a long and flat piece of ferromagnetic material with a magnetic strip embedded in it.
The basic theory of the present invention accordingly entails the use of a linear motor instead of the conventional drive mechanism consisting of a piston-and-cylinder mechanism. Linear motors will produce straight-line motions directly, without the intervention of transmissions. Force is accordingly exerted directly against the mass that is to be shifted. There are no intermediate mechanisms. Electrical energy is applied as such and need not be converted to another form.
Another advantage of a drive mechanism with a linear motor is that, in contrast to a piston-and-cylinder mechanism, which does not provide any forward motion until it has completed its stroke, both acceleration and braking can be very precisely controlled all through the stroke. The braking acceleration can for example be canceled or even reversed. A linear motor can accordingly generate an additional braking force, the strength of which can be established by the design of the carriage-braking means. As will be specified hereinafter with reference to the accompanying drawing, it will also be possible to dimension the motor and fasten it stationary to the carriage, ensuring that the motor""s secondary section separates from its stator during the braking phase. The reduced overlap will automatically decrease the motor""s forward impulsion.
When installed in a combat vehicle, the motor can be provided with electricity from a rechargeable battery supplied with current from the on-board power network. To ensure sufficiently rapid availability of enough power to effectively ram the shell, a temporary-storage reservoir with a capacity high enough to handle a single ramming procedure can be provided.
It will also be possible to mount electrical instruments and controls on the carriage to monitor the course if the procedure and provide additional power to the motor as needed.
This system of instrumentation also provides other advantages. It allows precise control of the distance traveled by the carriage as a function of time, of ramming rate as a function of elevation, and of propulsive force as a function of shell type, as well as of the braking procedure.
Various embodiments of a shell rammer in accordance with the present invention will now be specified with reference to the accompanying drawing, wherein